Static in C++

// file 1
static int x;
static void foo(){
		std::cout<<"hi\\n"<<std::endl;
}

static keyword makes the variable/function visible only to the members of the same c++ file this avoids collisions during linking. Unless we want a function or a variable to be linked externally we will should declare it as static.

On the other hand if we want a variable to be resolved externally we use extern keyword

extern int y; // will look for y in other files 

Static in C++ Classes

A Static Variable for a class is a common variable for the entire class and is the same for all instances of the class.

class hi{
public:
  static int x;
};
// int hi::x;
void solve(){
  hi h;
  cout<<h.x<<endl;
}

class hi{
public:
  static int x;
};
int hi::x = 11;
void solve(){
  hi h1,h2;
  h1.x = -1;
  cout<<h1.x<<endl;
  cout<<h2.x<<endl;
  // output-> -1 , -1
}

Static Methods

A static method much like the static variable belongs to class the rather than the object and can be called as ClassName::method() and hence it has no access to this→ pointer and also non static members of the class!

class MyClass {
public:
    static int staticVar;

    static void staticMethod() {
        cout << staticVar << endl;
    }
};

int MyClass::staticVar = 10;

Class functions basically get a hidden parameter which contains the data of the class while static methods don’t

Enum in C++

struct Color : int{
WHITE = 0,
GRAY, // = 1
BLACK // =2
};
struct Type : unsigned char{
WHITE = 5,
GRAY, // = 6
BLACK // = 7
};

Constructor in C++

class Hello{
	int x , y , z;
	public:
	Hello() : x(0) , y(0) , z(0) {
		//constructor works
	}
};

class Example{
public:
	Example(){
		cout<<"bann gaya with default"<<'\\n';
	}
	Example(int y){
		cout<<"bann gaya with " << y <<'\\n';
	}
}

class Entity{
private:
Example e1;
public:
/* Entity(){
	e1 = Example(8); // twice the constructor will be called 
} */

Entity(): e1(Example(8)){ // constructor called only once
}
}